1. Field of Invention
This invention relates in general to valve actuators, and in particular to a hydraulic actuator with a telescoping supply port.
2. Description of Prior Art
Valves can sometimes have a linearly translating member, such as a stem, to move the valve between the open and closed positions. Some valves, such as gate valves, have an aperture that aligns with the bore to allow flow through the valve. The valve can be normally open, and thus the valve is closed when it is moved linearly to push the aperture out of alignment with the bore. Alternatively, a valve can be normally closed, and thus the valve is opened when it is moved linearly to position the aperture into alignment with the bore. Regardless of whether the valve is normally open or normally closed, the valve can be actuated, or moved between the open and closed position, by a valve actuator.
Current valve actuators can have a piston located at the distal end of the valve actuator, opposite the end of the actuator that is connected to the bonnet of the valve assembly. The mass of the piston will affect the center of gravity of the valve actuator, which in turn affects the bending moment, stress, and fatigue on the connection between the valve actuator and the bonnet.